In the course of formulating the Machine to Machine (M2M) specification of the 3rd Generation Partnership Project (3GPP), a congestion control mechanism based upon an Access Point Name (APN) is specified and is also decided to be used for an APN congestion situation arising from a general User Equipment (UE).
It is specified in this mechanism that subscription data of a UE shall be stored at the network side for a period of time when an Attach/Tracking Area Update (TAU) request from the UE is rejected at the network side due to APN congestion.
Subscription information of a UE is stored in a mobility management context of the UE, and the value of storing the mobility management context has not been specified so far.
If the mobility management context is deleted at the network side too early, when the UE requests again for Evolved Packet System (EPS) Mobility Management (EMM)/EPS Session Management (ESM), a mobility management node, e.g., a Mobility Management Entity (MME), a Serving GPRS Support Node (SGSN), has no subscription information of the UE and thus have to interact again with a Home Subscriber Server (HSS)/a Home Location Register (HLR), thereby increasing signaling consumption; and if the mobility management node deletes the mobility management context too late, the context of the UE may be stored at the mobility management node for a too long period of time, thus increasing load at the network side.
In summary, the value of storing the mobility management context at the network side is not specified so far, and consequently signaling consumption and network load may be increased.